Our understanding of food webs transformed

Bug research conducted in Greenland shows that our assumptions regarding the structure of ecological communities may be seriously skewed.

Seven years ago, biologist Tomas Roslin left for Greenland to search for an insect community that would be as simple as possible. His intention was to explore how food webs are structured in real life.

“We easily fail to see the system of ecological interaction as a whole when the diversity of species grows,” says Roslin, who now works as university lecturer at the Viikki Campus.

Complicated connections

Roslin began the tremendous task together with ichneumon expert Gergely Várkonyi. The men chose butterflies living in north-eastern Greenland and the parasites specialising in them as the object of their study.

Usually, similar relationships between predators and their prey are studied by growing caterpillars in jars until the parasites attached to them develop into recognisable adults. However, bug species are much more connected to each other than this method has been able to reveal, shows a study newly published in PNAS.

“For instance, we noticed that several predatory species exploit more hosts than we had previously thought. This means that they are less specialised than presumed,” says Helena Wirta, the first author of the research report, from the Viikki Campus.

Barcoding the species

Thanks to new technology, researchers could make these surprising new discoveries.

The researchers used DNA barcodes to aid their work. These codes are identifiers based on variations of a specific gene and thus separate different species from each other.

“Our understanding of the structure of one of the world’s simplest food webs has been completely changed. We can just imagine what will happen when we study other environments through the same, precise method,” says Wirta.

Assisted by the barcodes, the researchers were able to identify the smallest of traces that one species had left in another.

“We were able to discover a parasite inside a caterpillar. Or from the gut of an adult parasite the remains of the host that it had consumed during its larval days,” says Roslin.

According to Várkonyi, almost all food webs contain predators that are difficult to locate.

Read the biography of a bug!

The idea about the DNA barcode was introduced a decade ago by Paul Hebert, whom Roslin, Wirta and the others were able to persuade to join their Greenland project.

“I believe that the new technology will transform our understanding of how nature works as a whole,” says Hebert.

“It may be that already in a couple of years we may catch any bug and obtain from it a DNA sequence for all the organisms that it has touched during its life. Identifying the bug’s history of interaction with other species allows us to specify the structures of ecological interaction with unparalleled precision.”